Cardiac stimulation devices (such as implantable pacemakers and implantable cardioverter-defibrillators (“ICDs”)) are generally capable of rectifying a patient's abnormal heart rhythm by delivering appropriately timed stimulation signals to one or more chambers of the heart, thereby causing the heart to contract in a synchronous pattern and better perform its primary function of blood circulation.
Cardiac stimulation devices that monitor or pace both the atrium and ventricle of the heart generally need to distinguish between atrial and ventricular events in order to employ the proper therapy with the appropriate timing. However, it is possible for ventricular events to be detected on an atrial detection channel, thus causing the implanted device to mistakenly interpret the detected signal as an atrial event and potentially deliver an erroneous pacing therapy in response. Ventricular events detected by the atrial channel are commonly referred to as “far-field R-waves” and usually are observable by the atrial channel shortly after the ventricular activity (due to propagation delay of the R-wave to the atria of the heart). A common technique for avoiding detection of far-field R-waves is to “blank” the atrial channel for a prescribed period of time during which far-field R-waves are expected to occur. The timing interval following an atrial event is generally known as a post-ventricular atrial blanking (PVAB) interval. The post-ventricular atrial blanking interval generally begins with the ventricular paced or sensed event, and all atrial events occurring the interval are, generally, neither detected nor counted in the various rate calculations. Once the post-ventricular atrial blanking interval has expired, the atrial channel can, if desired, be used to detect cardiac activity.
While the use of a post-ventricular atrial blanking interval is beneficial, a single predefined blanking interval may not be suitable for all patients and all circumstances. Also, it may not be convenient to identify the most suitable blanking interval for a given patient. It would therefore be advantageous, for example, to provide increased flexibility in a cardiac stimulation device with respect to blanking intervals, and further to provide convenient tools to physicians to assist determination of a blanking interval suitable for a particular patient.